Karachi, the financial heart of Pakistan, was shut down Wednesday because of political tension that followed various incidents of violence sparked by the arrest of a prominent politician in a crackdown on crime.

Nine people, including two policemen, were reported killed in the violence Tuesday. Trade suffered as shuttered shops and burning buses dotted parts of the city's landscape.

Only last week newly elected Prime Minister Nawaz Sharif had visited the country's largest and most populous city to ensure political unity in tackling the scourge of militant-backed crime rings and politically affiliated gangs.

There had been a rare show of inter-party unity backing the new government's drive to send Pakistan's paramilitary force, The Pakistan Rangers, into Karachi. But recent events could throw a wrench into this process as the arrest of a former member of parliament from the city's prominent MQM party has been linked to the death of the two policemen.

Speaking to CNN from London, MQM spokesman Muhammad Anwar called the incident "a travesty of justice" and said the Rangers' operation is politically motivated with a bias toward the PPP, former President Asif Ali Zardari's party, which now holds a majority in the provincial government of Sindh, where Karachi is located.

The operation started Thursday. According to information released by the Interior Ministry in the past 24 hours, three of the city's most wanted alleged target killers have been arrested.

Omar Hamid Khan, a spokesman for the interior minister, told CNN that the hostile reaction to the arrest is "temporary" and that there will always be "hiccups" but "the objectivity of the operation will not be lost sight of."